[JIT] clarify errors due to non-literal indexing into ModuleList, ModuleDict (#98606)
TorchScript only supports indexing into ModuleLists with integer literals. The error message already warns about this; but this PR adds clarifications around what a "literal" is. I'm adding this PR because, in my opinion, it's not obvious what a "literal" is and how strict its definition is. The clarification provided in this PR should make it easier for users to understand the issue and how to fix it.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/98606
Approved by: https://github.com/eellison, https://github.com/gmagogsfm
